1. Field of the Invention
The present invention relates to a magnetic circuit that constitutes a repulsive magneto-spring and is mounted on a suspension unit or the like.
2. Description of the Related Art
Various types of damping materials, dampers, and other control methods have been proposed to prevent vibration and noise that occur in machines and structures built from materials with low internal damping properties, which are required for their strength and rigidity.
Normally, springs and damping materials, such as metal springs, rubber, air springs, viscoelastic materials, and dampers, are combined to optimize vibration isolating properties. However, this combination often exhibits opposing characteristics, as in the relationship between dynamic magnification and loss factor. For that reason, many studies are being conducted on controlling vibration using passive vibration isolators including dynamic dampers, or quasi-active or active control systems. There is a demand for dampers which can cope with a characteristic change of an object for which vibration isolation is intended, or which is not subject to deterioration with age or influenced by the environment, such as temperatures, oils, ozone or the like.
In recent years, accompanying the practical use of permanent magnets that have a high coercive force and high residual magnetic flux density, research is flourishing in areas such as mechanical structures and magnetic systems that utilize magnetic levitation, magnetic bearings, dampers employing a magnetic fluid, etc., which use magnetic force and magnetic fluidity to control vibration. In particular, magnetic dampers in which eddy currents caused by electromagnetic induction and magnetic damping caused by the effects of magnetic flux are utilized and are useful as an attenuating means, and the practical use thereof is expanding.
The construction of an efficient magnetic circuit wherein a magneto-spring is constituted by repulsive permanent magnets is still open to further research. In the present, although the repulsive force of the magneto-spring is enlarged by increasing the size (thickness, opposing area and the like) of the magnetic circuit, there arises a problem in that the weight or cost of the magneto-spring is increased.
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a relatively inexpensive magnetic circuit that constitutes a repulsive magneto-spring having an increased repulsive force.
In accomplishing the above and other objectives, the magnetic circuit according to the present invention includes a yoke and a multi-pole magnet mounted on a predetermined surface of the yoke. The multi-pole magnet has magnetic poles formed in a direction perpendicular to the predetermined surface of the yoke. The multi-pole magnet is separated into two pieces. The magnetic circuit also includes a single-pole magnet interposed between the two pieces of the multi-pole magnet. The single-pole magnet has magnetic poles formed in a direction different from the direction in which the magnetic poles of the multi-pole magnet are formed. With this arrangement, the magnetic flux of the multi-pole magnet is controlled by the magnetic flux of the single-pole magnet, making it possible to provide an inexpensive magnetic circuit of a simple construction that can produce a large repulsive force.
Advantageously, the single-pole magnet is placed on a projection formed with the yoke on the predetermined surface thereof or on a spacer mounted on the predetermined surface of the yoke, and the two pieces of the multi-pole magnet are located on respective sides of the single-pole magnet. This arrangement can reduce the size of the single-pole magnet and provides an inexpensive magnetic circuit.
The two pieces of the multi-pole magnet adjoin the single-pole magnet with like magnetic poles opposed to each other on a side of the multi-pole magnet remote from the predetermined surface of the yoke, making it possible to further increase the repulsive force.
It is preferred that a two-pole magnet be used as the multi-pole magnet. With the use of the two-pole magnet, an increased repulsive force can be produced by a relatively inexpensive and simple magnetic circuit.